This invention relates to carburetors and, more particularly, to apparatus for venting fuel vapors from the fuel bowl of a carburetor.
Carburetor assemblies typically include one or more fuel bowls holding fuel, e.g., gasoline, that is supplied to the engine on which the carburetor is installed. The gasoline gives off vapors and the presence of these vapors in the fuel bowl or bowls creates an internal bowl pressure which may result in an overly rich air-fuel mixture being produced in the carburetor and combusted in the engine.
By venting fuel vapors from the fuel bowl or bowls, the internal bowl pressure is balanced with the outside air pressure and better control over the air-fuel mixture is achieved. However, fuel vapors are continuously produced even when the engine is off and if they are continuously vented they eventually saturate the air space adjacent the carburetor's air inlet or inlets. These vapors gravitate into the carburetor's air horn and the intake manifold of the engine and may displace the air in these regions. Consequently, when the engine is next started, an overly rich air-fuel mixture is supplied to the engine which makes it more difficult to start. Therefore, it is important that vapors be vented only while the engine is running.
Further, it is also important to insure that venting does occur when the engine is running. Most prior carburetor designs in which a fuel bowl vent is incorporated include only a single mechanism for opening the vent. If this fails, venting will not occur and the above-indicated problems will result.